Individual cylinder coolant control system and method

ABSTRACT

A coolant system and method for control of cylinder temperature in a multiple cylinder internal combustion engine includes an inlet rail for receiving coolant from a pump, an outlet rail located on a side of the cylinder head opposite the inlet rail and a plurality of individual coolant flow passages extending within the cylinder head and connecting the inlet rail with the outlet rail. A control valve and an associated temperature sensor are provided within each of the coolant flow passages and a controller individually controls each of the control valves in accordance with a signal received from its associated temperature sensor. The control valves may be controlled to bring the temperatures detected by their associated temperature sensors into conformance with an optimum temperature predetermined for engine speed and/or engine torque load.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention is cooling systems of internal combustionengines, specifically those with reciprocating pistons. The inventionprovides consistent controllable temperatures for each of the cylindersin a multi-cylinder engine.

2. The Prior Art

Conventional systems for cooling cylinder heads provide coolant patternswhich go generally from one end of the cylinder head and block to theother. The complicated coolant flow pattern that results is acombination of longitudinal flow and cross flow, but all cylinders arecooled together with a common coolant flow path.

The conventional approach is successful in that engines generally do notoverheat. However, the temperatures may vary between cylinders in a waythat some cylinders are cooled just barely enough, while other cylindersare overcooled. This difference in cooling can affect the distributionof fuel and air into the cylinders and the initiation of combustion,such that not all of the cylinders attain optimum performance due tocylinder-to-cylinder cooling differences.

Wilkinson—U.S. Pat. No. 5,058,535 teaches the use of a common railcooling system which directs coolant flow to individual cylinders offlat (180° vee) aircraft engines.

Wells—U.S. Pat. No. 4,601,265 disclose a common rail coolant routingsystem with an inlet common rail and an outlet common rail on the sameside of the cylinder block of an in-line engine. The system of Wells isdesigned to deliver equal amounts of coolant to each cylinder.

Haugen et al—U.S. Pat. No. 6,279,516 disclose a coolant cross-flowcoolant flow system which directs the coolant flow across the cylinderin two levels, essentially over, up, and out, and attempts to minimizeany flows between adjacent cylinders.

Abe et al—U.S. Pat. No. 5,386,805 teach a system having a separate inletand outlet rails for the coolant and also teaches the possibility ofusing a separate coolant flow pattern in the cylinder block (crossflow)which is different from the coolant flow pattern in the cylinder head.

Kasting et al—U.S. Pat. No. 4,284,037 disclose an engine coolant flowpattern which is substantially separate for each of the cylinders in amulti-cylinder engine. The approach of Kasting et al attempts to providean equal flow to each cylinder by a static structural design.

Bartolazzi—U.S. Pat. No. 5,975,031 teaches the use of a singletemperature sensor in a feedback control system for the fuel pump outputand/or the amount of coolant flow bypassed to the radiator.

Takahashi et al—U.S. Pat. No. 5,769,038 teach a design of the coolantflow pattern intended to deliver a uniform amount of coolant deliveredto each combustion chamber cooling area, in an attempt to provide equalcooling to the cylinders, without active control of the coolant flow.

Iwamoto et al—U.S. Pat. No. 4,665,867 teach a design of the coolant flowpassages on the inlet side of the coolant system that attempts toequalize the coolant flow to each cylinder of a multicylinder engine,without active control of the coolant flow to individual cylinders.

Nakanishi et al—U.S. Pat. No. 4,212,270 disclose the use of two coolingsystems, one for the cylinder head and the other for the cylinder blockof a multi-cylinder engine.

SUMMARY OF THE INVENTION

The present invention provides open-loop control of individual cylindercooling with control of the coolant flow to each cylinder provided bymultiple sensors (typically, one per cylinder) and individual cylindercoolant flow control valves. This active control of separate anddifferent coolant flows is in contrast to static designs for coolantflow control as exemplified by the Wilkinson, Wells, Kasting, Takahashiand Iwamoto references mentioned above.

The system of the present invention is an individual cylinder coolantcontrol system which includes an inlet common rail, an outlet commonrail, a coolant temperature sensor, and a coolant control valve for eachcylinder (fewer or more sensors and valves are also possible) and anoptional bypass valve to control coolant flow to the inlet common rail.The inlet common rail and/or the outlet common rail can be an integralpart of the cylinder head of the engine or be separate from it.

In the individual cylinder coolant control system of the presentinvention, the coolant flow is separate for each cylinder, each separateflow is actively controlled, the flow direction is across the cylinderhead, and the temperature of each cylinder is individually controllable.

Accordingly, the present invention provides a cooling system for anengine including a cylinder block having multiple cylinders covered andclosed by a cylinder head. The coolant system includes an inlet rail andan outlet rail located on opposing sides of the cylinder head and a pumpfor feeding coolant flow through a discharge line into the inlet rail. Areturn line serves to return coolant from the outlet rail to the otherportions of the cooling system and subsequently back to the pump, aplurality of individual coolant flow passages extend within the cylinderhead and connect the inlet rail with the outlet rail. A control valveand an associated temperature sensor are provided within each of thecoolant flow passages and a controller individually controls each of thecontrol valves in accordance with the signal received from itsassociated temperature sensor.

The present invention further provides a method for individuallycontrolling the temperature of each of multiple cylinders within acylinder block and covered by a cylinder head. The method involvespassing coolant through separate coolant flow passages, across thecylinder head, between an outlet rail and an inlet rail, sensing thetemperature within each of the coolant passages and adjusting andcontrolling flow through the coolant passage containing the temperaturesensor, responsive to a signal from the temperature sensor, to bring thesensed temperature for each of the coolant flow passages intoconformance with a predetermined optimum temperature. The method mayfurther include sensing engine load and/or engine speed and determiningan optimum temperature, as the predetermined temperature, in accordancewith the sensed engine load and/or engine speed. The method may furtherinclude directing the flow of coolant from a pump to bypass the inletand outlet rails and coolant flow passages, during warm-up of theengine, until a sensed temperature reaches a predetermined minimumvalue. The coolant flow passages may be entirely separate with onecoolant flow passage provided for each of the cylinders.

Preferably, a coolant flow passage is uniquely associated with each ofthe cylinders and the controller, individually for each cylinder,controls a control valve to bring the temperature detected by theassociated temperature sensor into conformance with a predeterminedoptimum temperature. The predetermined optimum temperature may be anoptimum temperature for a given load and/or engine speed stored in amemory readable by the controller.

Each of the coolant flow passages may be split so as to pass on both ofopposing sides of an exhaust valve, an inlet valve, and/or an ignitiondevice.

The coolant system preferably further includes a bypass rail forconnecting the discharge line to the return line, bypassing the inletand outlet rails and the coolant flow passages, and a splitter valve forselectively directing the discharge of coolant from the pump to theinlet rail and/or to the bypass rail.

Preferably, the coolant system has the inlet and outlet rails formedwithin the cylinder head.

Accordingly, the present invention provides the following advantagesover the prior art:

1. Independent control of the temperature of each cylinder of amulticylinder engine,

2. Rapid warm-up of the passenger compartment,

3. Improved cold-start and warmup efficiency,

4. Lower cold-start and warmup emissions, and

5. Improved warmed up efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a first embodiment of the system of thepresent invention.

FIG. 2 is a schematic diagram of a second embodiment of the system ofthe present invention.

FIG. 3 is a schematic diagram of a third preferred embodiment of thepresent invention.

FIGS. 4a-4 e show different configurations for the flow passage and flowpath between inlet and outlet rails for a single cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A schematic description of a first preferred embodiment, in the form ofa coolant circuit for a 4-cylinder engine cylinder head 10, is shown inFIG. 1. The system shown in FIG. 1, of course, can be adapted to engineswith any number of cylinders. Each of cylinders 1, 2, 3, and 4 hasassociated with it a flow control valve and a sensor. Thus, cylinder 1has a flow control valve 21 and a temperature sensor 11, cylinder 2 hasa flow control valve 22 and a temperature sensor 12, cylinder 3 has aflow control valve 23 and a temperature sensor 13, and cylinder 4 has aflow control valve 24 and a temperature sensor 14. The coolant systemfurther includes a water pump 5, a splitter valve 6, a radiator 8, and aheat exchanger (heater) 9 for heating the passenger compartment. A checkvalve 42 prevents backflow through heater 9 during warmup. Coolant flowfrom the inlet rail 30 to the outlet rail 32 is through separatechannels 61, 62, 63, and 64 formed within the interior of the cylinderhead 10 and extending across the cylinder head from an inlet rail 30 toan outlet rail 32.

When the engine starts up from cold, the splitter valve, which mayoperate like a conventional thermostat, directs all the coolant flowoutput from pump 5 through the bypass rail 34. Flow control valves 21,22, 23, and 24 are closed, and the coolant warms up rapidly in thecylinder head 10. When the temperatures indicated by temperature sensors11, 12, 13, and 14 are at appropriate levels, flow control valves 21,22, 23, and 24 are opened appropriate amounts to regulate thetemperature of each cylinder consistent with the optimum predeterminedvalue.

Although FIG. 1 shows the flow control valves 21, 22, 23, and 24 on theinlet side of the coolant flow path across the engine, alternativelythey could be located on the outlet side of the coolant flow path. Thetemperature sensors 11, 12, 13, and 14 are positioned in appropriatelocations within the cylinder head and may or may not be directly in thecoolant flow path.

A controller 48, having a memory 48′, serves to individually controleach of flow control valves 21, 22, 23, and 24 in accordance withsignals received from their respectively associated temperature sensors11, 12, 13, and 14. The controller 48 receives a signal related totorque or a torque signal from a torque load sensor 45 and/or an enginespeed signal from an engine speed sensor 47, applies the signal(s) to alookup table stored in memory 48′ to determine an optimum temperaturefor the sensed torque load and/or engine speed and individually controlseach flow control valve to bring the temperature sensed by itsassociated temperature sensor to the optimum temperature. Alternatively,the controller 48 may be adapted to compute an optimum temperature basedon the sensed engine speed and/or torque load.

A second embodiment shown in FIG. 2 has two water pumps 44 and 46 ratherthan a single water pump as in the first embodiment. The othercomponents of the second embodiment are the same as in the firstembodiment. The purpose of the additional water pump is to provide ahigher coolant flow rate to the cylinder head during times of greatthermal stress to the cylinder head such as in high engine speed or highengine torque operation. Provision of this additional cooling allows fora substantial increase in engine power, especially for short bursts, anddoes not penalize the engine due to an increase in parasitic powerrequired to drive a larger flow capacity pump when the extra coolantflow is not needed (most of the time). FIG. 2 shows a seriesconfiguration for the water pumps, but a parallel configuration is alsopossible.

In a third embodiment shown in FIG. 3, the coolant flow control valveand the coolant temperature sensor are integrated in each of units 71,72, 73, and 74 installed in the coolant flow on the outlet side of thecylinder head. This third embodiment provides packaging and costadvantages. The other components of the third embodiment are the same asthose of the first embodiment.

Additional embodiments of the invention can be divided into two classes:(1) embodiments for which the cooling flow circuit differs from theabove-described preferred embodiments and (2) embodiments for which thenumber of flow control valves per cylinder and the number of temperaturesensors per cylinder differ from 1.0

A. Embodiments Having Different Cooling Flow Circuits

The cooling flow for the cylinder block 40 can be provided in severalways, all of which arc compatible with this invention.

The coolant system for the engine block can be entirely separate fromthat for the cylinder head, including a different radiator, a differentcontrol approach, or even a different coolant medium including, but notlimited to, engine oil or transmission fluid. The coolant flow withinthe cylinder block in the entirely separate system can be conventionalor it can be a variant of this individual cylinder coolant controlsystem (ICCCS).

The coolant system for the engine block can be part of the same coolingsystem as the one for the cylinder head. In the “series configuration”shown in FIG. 1, the coolant flow, when the engine is warmed up, goesfrom the cylinder head 10 through heater 9, then to the cylinder block40, and then back to the radiator 8, the water pump 5, and the splittervalve 6.

As described above, the coolant from within the cylinder block can be ofa conventional nature or a variant of the individual cylinder coolantcontrol system of the present invention.

Another possible coolant flow configuration is a parallel path in whichthe flow exits the splitter valve 6 apportioned into flows to thecylinder head 10, the bypass line, and the cylinder block. The flowwithin the cylinder block can be of a conventional nature or of theICCCS type.

B. Embodiments for which the Number of Coolant Flow Control Valves PerCylinder and/or the Number of Temperature Sensors Per Cylinder are otherthan 1.0

The number of coolant flow control valves and/or the number oftemperature sensors per cylinder may be less than 1.0. As an example,consider the case for which there are two coolant flow control valvesand temperature sensors for a four-cylinder engine. In this case, theratio of coolant flow control valves and/or temperature sensors to thenumber of engine cylinders is 0.5. Various configurations with ratios ofcoolant flow control valves and/or temperature sensors to the number ofcylinders ranging from 0.0625 to 0.9375 are possible.

The number of coolant flow control valves and/or temperature sensors percylinder may also be greater than 1.0. As an example consider the casefor which there are two coolant flow control valves and two temperaturesensors for each cylinder of a four-cylinder engine. In this case, theratio of coolant flow control valves and/or temperature sensors percylinder is 2.0. The ratio of the number of the coolant flow controlvalves and/or the temperature sensors to the number of engine cylindersmay range from 1.01 to 3.0.

In all embodiments the individual coolant flow passages 61, 62, 63, and64, which traverse the cylinder head, can take any number of shapes. Forexample, each coolant flow passage could encircle (or nearly so) theexhaust valve seat(s) to provide extra cooling to that part of thecombustion chamber. The flow paths can be separate as illustrated in thedrawings or join each other as appropriate. They could also crossover/under each other.

The flow passages 61, 62, 63, and 64 could also encircle (or nearly so)the intake valve 71 seat(s), exhaust valve 72 seats, and/or providetargeted cooling to the ignition device 73, e.g., the spark plug or theglow plug of the engine. FIGS. 4a, 4 b, 4 c, 4 d, and 4 e show thegeometries of some of the geometrical pathways that the coolant flowcould take across the cylinder head. In each case, the coolant flow isdepicted entering the targeted cooling area at the bottom of the figure(COOLANT IN) and exiting the targeted cooling area at the top of thefigure (COOLANT OUT). Of course, this coolant flow could also bereversed.

The flow paths shown are illustrative of the options available with theindividual cylinder coolant control system of the present invention. Theconcept can apply to geometries other than those shown, to cylinderheads with more than two valves (i.e., 3 valves, 4 valves, 5 valves,etc.), and to cylinder heads where the spark plug shown is replaced by aglow plug or some other ignition device, such as those used in a Dieselengine.

Thus, the present invention offers the advantage that the cooling can betargeted toward areas that require more cooling, such as the exhaustvalve area. In addition, the individual cylinder controls allow forimproved overall control due to cylinder-to-cylinder variabilities inthe cylinder head manufacturing process which would result innon-uniform cooling using the prior art.

Operation

When the engine is started, the flow of coolant goes through thesplitter valve 6 and the bypass rail 34 and back to the radiator 8 andpump 5, thus bypassing the cylinder head 10, the cylinder block 40 andthe passenger compartment heater 9. The cylinder head 10 warms upquickly since no coolant flow is removing heat transferred through thecylinder walls. When the cylinder head temperature sensors 11, 12, 13,and 14 indicate that coolant temperature is appropriate, the splittervalve 6 opens, permitting flow of coolant into the inlet common rail 30,and across the cylinder head 10 to the outlet common rail 32. Theoutputs from the cylinder head temperature sensors go to the controller48 which adjusts the individual cylinder control valves 21, 22, 23, and24 to adjust coolant flow to each cylinder so that the same appropriatetemperature is obtained for the coolant exiting each coolant flowpassage.

Two examples of possible control approaches are: (1) equal temperatureand (2) performance based. As an example of the equal temperaturecontrol approach, the best cylinder temperature for a given engine loadand speed, as detected by torque detection means 45 and speed sensor 47,respectively, is predetermined and is stored as a look-up table inmemory 48′. The controller 48 adjusts the coolant flow valves for eachcylinder to produce the same (optimum) temperature for each cylinder,thus guaranteeing optimum performance.

In the performance-based system, the control of the temperature is usedto optimize a dynamically determined performance measure. For example,in a system with individual cylinder pressure sensors, it would bepossible to determine the location of peak pressure for each cylinder.For a given engine and combustion system, the location of peak pressureat which optimum efficiency occurs can be pre-determined. Usually, thebest value for this performance measure is in the range of 10° to 15° ofcrankshaft motion after top dead center on the powerproducing stroke ofthe cylinder. In such a system the controller would control the coolantflow across the cylinder head in each cylinder so that the location ofpeak pressure in each cylinder is at the optimum value, even if thecylinder temperatures in the different cylinders are not the same.

Applications in General

The individual cylinder coolant control system (ICCCS) of the presentinvention improves the performance of all three engine types: sparkignition, Diesel, and HCCI, by enhancing faster cylinder head warmup.This improves the fuel consumption performance of the engine and reducesexhaust emissions which arc a result of excess fuel metered to thecylinder in starting and warming up the engine.

When the engine is started up, the coolant flow bypasses the cylinderhead. With no cooling flow, the cylinder head warms up more quickly thanit would if cold coolant were circulating through it. No controls areneeded for the water pump.

The individual cylinder coolant control system of the present inventionpermits individual temperature control of each cylinder in the engine,since coolant flow can be adjusted to each cylinder to have allcylinders operating at the same conditions, thereby improvingcylinder-to-cylinder combustion and power and allowing for smootherengine operation.

The efficiency of a spark-ignition engine is strongly a function ofspark timing, the time relative to the piston's motion on thecompression stroke when the ignition system causes a spark to jump thegap in the spark plug. However, the best efficiency spark timing cannotbe reached for some conditions because of spark knock. Parts of theunburned mixture become too hot during the compression of the unburnedmixture by the burned mixture. However, in accordance with the presentinvention, the temperature of the combustion chamber in each cylindercan be controlled and lowered near these knock-prone points to provide aspark timing resulting in better efficiency. In contrast, currentengines do not achieve the best spark timing in each cylinder due tocylinder-to-cylinder cooling differences.

Application to Diesel Engines

High efficiency diesel engines have drawbacks when it comes to heatingthe passenger compartment, since heat rejected to the coolant is usedfor heating the passenger compartment.

During the warm up process, cold coolant circulates but bypasses theheat exchanger used to provide heat for the passenger compartment. Theamount of coolant in the cylinder head is small, compared to the totalcoolant volume, so it warms up quickly. Adjusting the coolant flowacross the cylinder head provides optimum temperatures to the coolantside of the passenger compartment heat exchanger for fast warmup of thepassenger compartment since the heat exchanger is positioned to receivethe coolant just after it is heated up by cooling the cylinder head.

Application HCCI Engines

Control of the temperature of the intake charge prior to theautoignition which is characteristic of HCCI combustion is the mostimportant control parameter for this combustion type.

The ICCCS of the present invention can vary the combustion chambertemperature in each cylinder so that all of the cylinders are undergoingHCCI combustion, and, in addition, undergoing HCCI combustion at thesame time so that the heat release for each cylinder is timed foroptimum engine efficiency. This can be done in an open loop manner, orthe ICCCS system can be adapted to control in a feedback loop using, forexample, a sensor in each cylinder that gives a response that can beused to determine the location of peak pressure in that cylinder.Control valves can be adjusted to ensure that the peak pressure locationis optimum for each cylinder.

The ICCCS is highly advantageous for HCCI combustion since the coolantflow to each cylinder can be changed rapidly.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative, and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

I claim:
 1. A coolant system for an engine including a cylinder blockhaving multiple cylinders formed therein, and a cylinder head, saidcoolant system comprising: an inlet rail and an outlet rail located onopposing sides of the cylinder head; a pump for feeding a coolant flowthrough a discharge line into the inlet rail; a return line forreturning the coolant from the outlet rail to the pump; a plurality ofindividual coolant flow passages extending within the cylinder head andconnecting the inlet rail with the outlet rail; a control valve and anassociated temperature sensor within each of said coolant flow passages;a controller for individually controlling each of said control valves inaccordance with a signal received from its associated temperaturesensor.
 2. The coolant system of claim 1 wherein each of said pluralityof coolant flow passages is uniquely associated with a single one ofsaid cylinders and wherein said controller, individually for eachcylinder, controls a control valve to bring the temperature detected bythe associated temperature sensor into conformance with a predeterminedoptimum temperature.
 3. The coolant system of claim 2 wherein theoptimum temperature is predetermined for engine load and/or enginespeed.
 4. The coolant system of claim 1 wherein the cylinder head has,mounted therein, at least paired intake and exhaust valves associatedwith each of the multiple cylinders and wherein a coolant flow passageis split and passes on both of opposing sides of said exhaust valve andone branch of the split coolant flow passage passes between the pairedintake valve and exhaust valve, in passage across the cylinder head fromthe inlet rail to the outlet rail.
 5. The coolant system of claim 4wherein said coolant passage split to pass an exhaust valve on bothopposing sides is further split to pass on opposing sides of the intakevalve paired with the exhaust valve.
 6. The coolant system of claim 1wherein the cylinder head has, mounted therein, at least paired intakeand exhaust valves and an ignition device associated with each of saidmultiple cylinders and wherein a coolant flow passage is split andpasses on both of opposing sides of the ignition device.
 7. The coolantsystem of claim 6 wherein said split coolant flow passage is furthersplit to pass on one or both sides of the paired exhaust valve.
 8. Thecoolant system of claim 7 wherein said split coolant flow passage isfurther split so as to pass on both of opposing sides of the pairedintake valve.
 9. The coolant system of claim 1 further comprising abypass rail for connecting the discharge line to the return line,bypassing said inlet and outlet rails and said coolant flow passages,and a splitter valve for selectively directing the discharge of coolantfrom said pump to said inlet rail and/or to said bypass rail.
 10. Thecoolant system of claim 1 wherein said inlet rail and said outlet railare formed within said cylinder head.
 11. The coolant system of claim 1wherein said fluid flow passages are separate so that there is no fluidcommunication therebetween other than through said inlet and outletrails.
 12. The coolant system of claim 1 further comprising a passengercompartment heater in said return line and wherein coolant exiting theoutlet rail flows, in succession, through the passenger compartmentheater and through a coolant jacket of the cylinder block.
 13. A methodfor controlling cylinder temperature in a multiple cylinder internalcombustion engine including feeding coolant through a discharge line toa plurality of individual coolant flow passages extending within acylinder head of the internal combustion engine, wherein the individualcoolant flow passages traverse the cylinder head between an inlet railreceiving the coolant from a pump and an outlet rail, and individuallycontrolling coolant flow through each of the flow passages in accordancewith a signal received from a temperature sensor which senses thecoolant temperature within that coolant flow passage.
 14. The method ofclaim 13 further comprising detecting torque load on the internalcombustion engine, determining an optimum temperature for the detectedtorque load and controlling coolant flow through each of the pluralcoolant flow passages to bring the temperature detected for each coolantflow into conformance with the optimum temperature.
 15. The method ofclaim 14 wherein the detected torque load is applied to a tablecontained in memory to determine the optimum temperature.
 16. The methodof claim 14 additionally comprising detecting engine speed andcontrolling coolant flow through each of the coolant flow passages inaccordance with the detected engine speed, detected torque load andsignal received from a temperature sensor associated with a coolant flowpassage.
 17. The method of claim 13 further comprising detecting enginespeed, determining an optimum temperature for the detected engine speedand controlling coolant flow through each of the coolant flow passagesto bring the temperature detected for that coolant flow passage intoconformance with the optimum temperature.
 18. The method of claim 17wherein the detected engine speed is applied to a table stored in memoryto determine an optimum temperature and the coolant flow through each ofthe plural coolant flow passages is controlled to bring the temperaturedetected for that coolant flow passage into conformance with thedetermined optimum temperature.
 19. The method of claim 13 additionallycomprising bypassing the coolant flow passages, during warm-up of theinternal combustion engine, until at least one detected temperaturereaches a predetermined minimum value.
 20. The method of claim 13additionally comprising splitting each of the coolant flows through theplurality of coolant flow passages so that each individual coolant flowpasses on both of opposing sides of an exhaust valve, an inlet valveand/or an ignition device of a cylinder.